The present invention relates to a hand-held transmitter for emitting coded electromagnetic pulses to a receiver for receiving pulses emitted by the transmitter, and to a method of coding electromagnetic pulses. The transmitter may comprise a current/voltage supply, a coded pulse generating coding unit with an adjustable code, a pulse shaper, and HF oscillator, an HF output stage, a filter and an antenna.
The associated receiver for receiving coded electromagnetic pulses may comprise a current/voltage supply, an antenna, an integrated receiver comprising HF and IF amplifier stages and a mixer for intermediate frequency generation, a demodulator, a signal amplitude regulating system, a decoding unit with a code-selector circuit and an input/output circuit (interface).
A transmitter-receiver system consisting of such a transmitter and an associated receiver can be used for the remote operation of various items of equipment. Preferably, such transmitter-receiver systems are used for the remote controller operation of garage doors or entrance gates, the transmitter being carried in the car and operated by the driver or passenger. In such a case, only a few functions are generally required, for example one switch or button for "open" and one for "close".
When the transmitter is operated, e.g. by pressing a button marked "open", the transmitter emits a sequence of electromagnetic pulses which corresponds essentially to a binary code number, one of the bits emitted in the form of electromagnetic pulses corresponding to the desired function, in other words, in the selected example, the opening of the garage door. The other bits (for example 10) can be individually set at the transmitter, the associated receiver comprising a decoding unit with an analogue bit adjustment facility, the setting having to coincide with that of the transmitter, when the desired function (e.g. "open" or "close") is to be triggered. Therefore the receiver converts the sequence of electromagnetic pulses emitted by the transmitter into binary numbers, relates (at least) one of the bits to a specific function and compares the other bits which form, so to speak, a code word with the bit setting of the decoding unit. Only if the emitted binary code word coincides with the code word to which the decoding unit is set will the desired function by triggered.
Such a binary code word can be represented as a specific sequence of the digits 0 and 1. Since the transmitter and receiver have to have the same code word, the probability that--to stay with the example of the garage doors--when a transmitter is operated in front of the garage door, the associated receiver will also simultaneously open or, as the case may be, close one or even more garage doors at neighbours' houses and possibly still within the range of the transmitter, is avoided. A hitherto constructed transmitterreceiver system comprises a code word with a word length of 12 bits, producing a total of some 4096 different possible code settings. This system can likewise co-operate with equipment according to the present invention.
A filter and a pulse shaper are necessary components of the transmitter, in order to avoid the transmitter sending out interference pulses and in order to restrict the required HF band width, which would make it impossible to obtain regulatory agency approval necessary for operating the transmitter.
It goes without saying that a receiver can receive and convert transmitted pulses from a plurality of transmitters so long as the latter only emit the corresponding coded sequence of pulses. As garage and entrances are often used by a number of different persons, therefore, each of these persons can carry his own transmitter with him in the car or in his pocket and use the transmitter to operate the gate or garage door. This is particularly true in the case of relatively large garage installations or underground garages which are jointly used by a number of local residents. If the transmitter is to be carried not only in the car but, for example, also in the hand or in a jacket or trouser pocket comfortably, then it is very important for it to be of small overall size and to be of low weight. Hitherto, only a relatively small number of installations intended for the purpose have been equipped with corresponding receivers and transmitters. In addition to reducing the size of the transmitter, therefore, it is also desirable to simplify the constrcution of receiver and transmitter and to reduce manufacturing costs. This has not as yet been possible, however, with the hitherto known transmitter-receiver system to any adequate degree.
Therefore, the present invention is based on the problem of providing a transmitter and a receiver having the features mentioned at the outset, but which can be more economically produced and to smaller dimensions, the functional reliability of the past being at least retained but being, as far as possible, enhanced.